INHIBITION BY HALOTHANE OF POTASSIUM-STIMULATED ACETYLCHOLINE-RELEASEFROM RAT CORTICAL SLICES

I Cholinergic neurones in the basal forebrain are linked to cortical a ctivation and arousal. 2 The present study was designed to examine the hypothesis that clinically relevant doses of halothane (0.1 to 5%) wo uld significantly reduce depolarization-evoked acetylcholine (ACh) rel ease from rat cortical slices. 3 ACh release was measured from rat cor tical slices by a chemiluminescent technique. 4 Depolarization-evoked ACh release was inhibited significantly by halothane with an IC50 of 0 .38%. This value equates to 0.3 MAC (the minimum alveolar concentratio n at which no movement occurs to a standard surgical stimulus in 50% o f subjects) for the rat. 5 The potent effect of halothane on ACh relea se suggests that this mechanism may be a target for the action of vola tile anaesthetic agents. This in vitro effect on ACh release is consis tent with effects of halothane reported in vivo.